The present invention relates to a false twist yam, a production method thereof, and a production apparatus thereof.
False twist yams of the invention have little cross sectional deformation, and have such features as good drape properties, soft feeling, bulky feeling, and lightweight feeling, as well as a desirable degree of stretch, strong-kneed, and repulsion feeling. A cloth comprising false twist yarns of the invention has mild luster that cannot be achieved with conventional yarns, and possesses a smooth, dry feeling.
With good mechanical and other properties, synthetic fibers have been used in goods in a large variety of fields including ordinary apparel.
Efforts in the field of apparel production have been made with the aim of providing improved synthetic fibers that are similar to natural material. Drawn yarns, in particular, tend to lack bulkiness, and to solve this problem, improved false twist yarns have been developed and manufactured in a process in which yarns are false-twisted while being drawn to achieve a desirable bulkiness.
To provide lightweight material, hollow fibers that consist of hollow single yarns have been developed and manufactured.
To provide fabrics having dry-feeling by reducing contact area between filaments, filament having a noncircular cross section of which the peripheral figure is wavy, have been manufactured. However, there are limits to being able to produce such a wavy form by a spinning process. If such filaments having noncircular cross section are false-twisted to produce false twist yarn, woven or knit fabric manufactured from the false twist yarns tends to have problems such as sandy touchable feeling or lack of soft feeling. In addition, the wavy form is deformed largely during the false twisting process, preventing the wavy form from having good effect on the resultant woven or knit fabrics.
False twist yarn produced by false twisting hollow filaments tend not to achieve required lightweight properties because of substantial destruction of hollow portions.
False twisting has to be performed at a high temperature to produce material that maintains sufficient bulkiness and crimp properties, but high-temperature processing tends to reduce the shrinkage percentage of the resultant false twist yarn.
JP 01-314740 A discloses a technique that aims to widen the range of the shrinkage percent level and reduce the cross sectional deformation of the resultant yarn. JP 01-183540 A discloses a technique that aims to produce high density woven fabric from a yarn having a small cross sectional deformation and a high shrinkage.
Under these techniques, however, filaments are false-twisted while being heated below the glass transition temperature, and therefore the techniques are low in productivity for false twist yarn and are not suited for commercial production.
In most conventional processes for out-drawing and false texturing or in-drawing and false texturing of synthetic fiber yarn, a twisted yarn is heated first, and then drawn, twisted, and heat-set, followed by untwisting.
In the conventional false twisting processes described above, a false twisting apparatus comprising a feed roller, a take-up roller, a heating plate provided between both rollers and a means of false twisting, is used.
If the false twist processing speed is increased in the false twisting apparatus, the twisting tension increases or the yarn is twisted on the heating plate, and an extension break of single filament in the yarn or a heat deterioration of the yarn that results in fluffing or scission of filaments is observed. It becomes necessary to extend the length of the heating plate to compensate for reducing the heat setting time.
To solve this problem, JP 09-20034 A proposes a method in which a yarn is entangled before being fed to a false twisting apparatus, and heated before being twisted by using a feed roller as a heating roller, followed by false twisting which is performed by using a nip roll as disclosed in JP 49-132353 A in such a manner that twisting starts at the end point of heating on the heating roller.
In this method, however, the starting point of twisting on the yarn is in contact with the surface of the heater, and the nip roll is used, which tends to cause problems such as heat deterioration and abrasion of the yarn on the surface of the heater, and wearing and deterioration of the nip roll which will result in retroaction of twist toward the heating roller and, in turn, fluffing and scission of the yarn. These problems can be very serious in the case of a yarn comprising ultra fine filaments or a synthetic fiber yarn comprising filaments having a special cross sectional shape.
Furthermore, a false twist yarn produced by the conventional process has a high crimp appearance property, and where a cloth is produced from such yarn, shrinkage of the yarn takes place at the time of appearance of crimps during the process of relaxation, presetting, denier reduction or dyeing, causing deterioration in drape properties, bulkiness, or soft feeling.
To solve these problems, the so-called xe2x80x9cdouble-heating false twistingxe2x80x9d process has been widely used, in which the yarn is false-twisted by the above-mentioned conventional technique, followed by further heat-setting of the resultant yarn using a heating plate.
Each of JP 59-130336 A and JP 60-252738 A discloses a technique in which an undrawn polyester yarn is false-twisted at a low temperature.
Each method, however, cannot solve the problem of the deterioration in drape properties, bulkiness, or soft feeling of fabrics due to shrinkage that takes place during the development of crimps.
In most conventional processes for production of synthetic fiber yarns, particularly drawn ones, a spindle-type winder is used to wind up the yarn in a pirn form on a bobbin in order to improve the pulling or rewinding properties of the yarn at the time of pulling out yarn from the bobbin to feed it to a twisting process or a weaving machine. In such a pirn-winding bobbin, a top pirn wind is formed at a top portion of the bobbin away from the pirn portion so that a location of the end of the yarn is found easily when using the bobbin.
When a top pirn wind is formed after winding up a false twist yarn in a pirn form, however, the yarn processing speed is decreased and the heat history of the yarn is affected during the formation of the top pirn wind, resulting in coexistence of yarns with different crimp properties. Thus, yarns with undesirable crimp properties have to be removed, causing a problem with the need of a complicated production process.
An object the present invention is to provide a false twist yarn that is free from the above-mentioned disadvantages of the conventional art, and is able to serve to produce woven fabrics or knit fabrics (hereinafter referred to as xe2x80x9cwoven/knit fabricsxe2x80x9d) that have such features as good drape properties, soft feeling, bulkiness, and lightweight properties, as well as rich in stretch, kneed and repulsion feeling and can form cloth with mild luster and a smooth, dry feeling to achieve a feeling different from conventional drawn or false twist yarns, and a production method and a production apparatus therefor.
To accomplish that object, a false twist yarn of the invention consists of (i) a synthetic fiber yarn and has the following properties (ii)-(vii).
(ii) an elongation (EL) of not less than 20% and not more than 50%,
(iii) a crimp rigidity (CR) of not less than 10% and not more than 40%,
(iv) a crimp appearance stretch ratio (TR) of not less than 0.5% and not more than 15%,
(v) a dry heat shrinkage stress maximum value (MCS) of not less than 0.1 cN/dtex and not more than 1.0 cN/dtex,
(vi) a deformation degree of single filament (SDD) of not less than 1.0 and not more than 2.5, and
(vii) an entanglement number (EN) of not less than 4 and not more than 50.
It is preferable that the false twist yarn of the invention has a real twist number (RT) of not less than 4 t/m (turns/meter) and not more than 15 t/m.
It is preferable that each of filaments forming not less than 30% of the false twist yarn of the invention has a hollow percentage (HR) of not less than 6% and not more than 15%.
It is preferable that the false twist yarn of the invention comprises a mixture of filaments whose peripheral profile of cross section has no concave portions and whose peripheral profile of cross section has concave portions, the deformation degree (SDD) of the filaments having no concave portions being not less than 1.0 and not more than 2.0, and a deformation degree (SDD) of the filaments having concave portions being not less than 1.6 and not more than 2.5.
It is preferable that the false twist yarn of the invention is wound up in a pirn form on a bobbin and the starting portion of winding of the yarn and the finishing portion of winding of the yarn are held by at least one yarn gripping means provided on the bobbin.
To accomplish that object, a method for producing a false twist yarn according to the invention is as follows.
A method for producing a false twist yarn comprises (i) an undrawn yarn feeding process that feeds an undrawn synthetic fiber yarn, (ii) a drawing and false twisting process that draws and false-twists the undrawn yarn fed from the undrawn yarn feeding process, and (iii) a false twist yarn winding process that winds up the false twist yarn produced by drawing and false twisting performed in the drawing and false twisting process, wherein (iv) the drawing and false twisting process contains a heater, a false twisting means, and a twist stopping means provided between the heater and the false twisting means, the undrawn yarn is heated by the heater while twisting motion imparted by the false twisting means on the undrawn yarn is restrained by the twist stopping means, and subsequently the heated undrawn yarn, after passing through the twist stopping means, is false-twisted by the false twisting means with a starting point of twisting formed by the twist stopping means.
It is preferable that in the method for producing a false twist yarn of the invention, an entangling process that imparts tangles of filaments in the undrawn yarn, before the heating of the undrawn yarn by the heater is provided.
It is preferable that in the method for producing a false twist yarn of the invention, the fineness of filament (SD) in the undrawn yarn is not more than 1.2 dtex.
It is preferable that in the method for producing a false twist yarn of the invention, the undrawn yarn comprises at least two types of filaments with different cross sectional shapes.
It is preferable that in the method for producing a false twist yarn of the invention, a reheating process in which the yarn after passing through the twist stopping means is reheated between the twist stopping means and the false twisting means is provided.
It is preferable that in the method for producing a false twist yarn of the invention, a spindle having a vertical rotation axis, a bobbin mounted on the spindle, a yarn guide that rotates outside the bobbin to guide the false twist yarn onto the bobbin and a traverse guide that moves the yarn guide up and down along the rotation axis of the spindle to form a pirn on the bobbin and that produces yarn end portions on the bobbin at the starting and finishing of winding of the false twist yarn are provided in the false twist yarn winding process, and the starting and finishing portions of the false twist yarn are held by a yarn gripping means provided on the bobbin at positions corresponding to the positions of the starting and finishing portions of winding of the false twist yarn.
To accomplish that object, an apparatus for producing a false twist yarn according to the invention is as follows.
An apparatus for producing a false twist yarn comprises (i) an undrawn yarn feeding means that feeds undrawn synthetic fiber yarns, (ii) a drawing and false twisting means that draws and false twists the undrawn yarns fed from the undrawn yarn feeding means, and (iii) a false twist yarn winding means that winds up the false twist yarn produced by the drawing and false twisting performed by the drawing and false twisting means, wherein (iv) the drawing and false twisting means contains a heater, a false twisting means, and a twist stopping means provided between the heater and the false twisting means, the undrawn yarn is heated by the heater while twisting motion imparted by the false twisting means on the undrawn yarn is restrained by the twist stopping means, and subsequently the heated undrawn yarn, after passing through the twist stopping means, is false-twisted by the false twisting means with a starting point of twisting formed by the twist stopping means.
It is preferable that in the apparatus for producing a false twist yarn of the invention, an entangling means that imparts tangles of filaments in the undrawn yarn, is provided at a position before the heating of the undrawn yarn by the heater.
It is preferable that in the apparatus for producing a false twist yarn of the invention, a reheating means in which the yarn after passing through the twist stopping means is reheated between the twist stopping means and the false twisting means is provided.
It is preferable that in the apparatus for producing a false twist yarn of the invention, the false twist yarn winding means includes a spindle having a vertical rotation axis, a bobbin mounted on the spindle, a yarn guide that rotates outside the bobbin to guide the false twist yarn onto the bobbin, and a traverse guide that moves the yarn guide up and down along the rotation axis of the spindle to form a pirn on the bobbin and that produces yarn end portions on the bobbin at the starting and finishing of winding of the false twist yarn, and the starting and finishing portions of the false twist yarn are held by a yarn gripping means provided on the bobbin at positions corresponding to the positions of the starting and finishing portions of winding of the false twist yarn.